1. Field of the Invention
The present invention relates to an improved sample cell useful with fluorescent X-ray analytical devices employing X-ray flouorescence as the method of detection.
2. Description of the Prior Art
A typical sample cell for use with fluorescent X-ray analytical devices is disclosed in U.S. Pat. No. 4,037,190 granted July 19, 1977. The sample cell shown in such patent includes telescopically interfitting parts molded from synthetic plastics such as nylon, polypropylene, or polyester. When the parts of such sample cell are fitted together they support a radiation permeable membrane so as to define a liquid sample-receiving surface. The liquid sample is analyzed and thereafter the plastic parts of the sample cell are discarded.
A more recent sample cell of this nature utilizes a cup and a ring which is telescopically slideably received by the exterior of the cup, with a radiation permeable membrane being sandwiched therebetween so as to be tightly stretched across the cup to thereby present a uniform flat surface to the received radiation when inverted. The cup and ring members are formed of polyethylene. This type of sample cell utilizes fewer parts than the sample cell disclosed in U.S. Pat. No. 4,037,109. It has been found, however, that in order to tightly and uniformly stretch the membrane across the top of the cup, the cup and the ring must be tightly interfitted. In view of the tight-fitting relationship between the cup and the ring, the membrane tends to bind over the lip of the cup and often either tears or puckers. To overcome this problem, it has been proposed to apply a lubricating film to the mating surfaces of the cup and the ring. A considerable amount of time however, is required to apply lubricant to the cup since it is essential that the lubricant not contact the interior of the cup so as to contaminate the liquid samples received therein. This type of sample cup also utilized a parting line on the cup adjacent to the lip of the cup. The presence of such parting line at that point was found to contribute to breakage of the membrane on the sharp edge defined by the parting line.